The irresistible—and destructive—power of unbridled passion is the theme of Catherine Breillat’s “The Last Mistress,” which she adapted from a 1851 novel by Jules-Amedee Barbey d’Aurevilly. Her treatment of the tale of a handsome but impecunious young nobleman, his wealthy and beautiful new wife, and the voluptuous older woman who’d been his mistress for a decade before his marriage is visually quite explicit when it comes to the numerous scenes in which the attractive leads remove their handsome period costumes and take to bed together—often in poses so artfully arranged and languidly played that that they have a painterly feel.

Elsewhere, it must be said, Ms. Breillat’s approach is more prosaic: the compositions are mostly pedestrian, the pacing sometimes turgid rather than evocatively deliberate, and the performances occasionally stilted and tentative. But her film is nonetheless a gripping one, its very lack of directorial virtuosity having a curiously mesmerizing effect (though some might call it soporific). And it boasts one show-stopping turn, from Asia Argento as the volatile, aggressive, emotionally uncontrolled Spanish woman called Vellini. Despite the apparent limitations of Breillat as a filmmaker, she certainly manages to get a true performance from an actress who, under her own father’s direction, came across so amateurishly is “Mother of Tears” not long ago.

The film opens in 1835, during the rule of “Citizen King” Louis-Philippe, as impossibly good-looking Ryno de Marigny (Fu’ad Ait Aattou) is about to wed the virginal blonde Hermangarde (Roxane Mesquida), granddaughter of the saucy old Marquise de Flers (Claude Sarraute). The marquise’s fussy friend, the Comtesse d’Artelles (Yolande Moreau), who knows of the young man’s long relationship with the notorious Vitelli, sends a common acquaintance, the lascivious old rake the Vicomte de Prony (Michael Lonsdale), to confront Vitelli, but as it turns outs he needn’t have bothered: Ryno has determined that after one last visit to his mistress he will break it off conclusively and be faithful to his bride.

And that is certainly what he tells the marquise when the wily old woman confronts him one night and has him recount to her the history of his decade-long affair. In a flashback that takes up a good portion of the picture, he describes how, when he first saw the woman, then the wife of an elderly British aristocrat (Nicholas Hawtrey), he dismissed her as “a ugly mutt” but soon became obsessed with her despite—or perhaps because of—her ostentatious disdain for him. His unwanted attentions resulted in a duel with her husband in which the younger man, refusing to take proper aim, was seriously wounded—which made her as suddenly lustful for him as he’d been for her. (A scene in which she bursts into his bedroom as a physician is extracting the bullet from his chest is shocking—and it’s impossible to tear your eyes from it.) Soon Marigny, restored to health, fathered a child by her and the three were living in North Africa; but when the girl died, they returned to France and kept up an on-and-off affair based on nothing except for unreasoning passion. But love—Marigny assures the marquise—was not a factor, and will impede his fidelity.

Satisfied—indeed, enthralled by the story—the marquise allows the wedding to go forward, and presently the newly-married couple is living happily at a seaside castle in the provinces, with Hermangarde getting pregnant, until Vitelli arrives to tempt Marigny back to his old ways.

There’s an obvious sense of fatalism to “The Last Mistress” (or, as the title would be more accurately but less kindly translated, “The Old Mistress”), but though the film definitely has a tragic dimension, true to tell it never goes very deep in that respect. And there’s a lurid quality to it, though with its air of nineteenth-century rigidity and the period artistic overlay it would be hard to characterize as sensationalistic. Rather what it achieves is the same sort of near-flippancy about serious matters that marks so much cynical French literature of the mid-nineteenth century. It’s provocative but deliberately unrealistic, staid but at times wildly over-the-top. And because of this dualistic quality, it’s fascinating.

Argento’s flamboyance drives the picture, but in terms of sheer beauty she’s definitely thrown into the shade by Aattou, who isn’t much of an actor (and doesn’t seem entirely comfortable with the hats he has to wear) but is certainly a presence (even though he looks awfully young to have been having an affair for a decade when we first meet him). And while Mesquida makes a gorgeous young bride, she’s terribly stiff. To compensate, the oldsters—Sarraute, Moreau and Lonsdale—are all delightful. And the trappings—costumes, locations, props—are all finely chosen, with Yorgos Arvanitas’ cinematography taking it all in. The sporadic bits of classical music fit, too.

At once austere and extravagant, “The Last Mistress” is a dispassionate autopsy of a passionate triangle, brilliantly devised if not always perfectly executed.